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>ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR</TITLE
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>Video for Linux Two API Specification: Revision 0.24</TH
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><H1
><A
NAME="VIDIOC-G-MODULATOR"
></A
>ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN11434"
></A
><H2
>Name</H2
>VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR&nbsp;--&nbsp;Get or set modulator attributes</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN11438"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><P
></P
><A
NAME="AEN11439"
></A
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int ioctl</CODE
>(int fd, int request, struct v4l2_modulator
*argp);</CODE
></P
><P
></P
></DIV
><DIV
CLASS="FUNCSYNOPSIS"
><P
></P
><A
NAME="AEN11449"
></A
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int ioctl</CODE
>(int fd, int request, const struct v4l2_modulator
*argp);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN11459"
></A
><H2
>Arguments</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><CODE
CLASS="PARAMETER"
>fd</CODE
></DT
><DD
><P
>File descriptor returned by <A
HREF="r14090.htm"
><CODE
CLASS="FUNCTION"
>open()</CODE
></A
>.</P
></DD
><DT
><CODE
CLASS="PARAMETER"
>request</CODE
></DT
><DD
><P
>VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR</P
></DD
><DT
><CODE
CLASS="PARAMETER"
>argp</CODE
></DT
><DD
><P
></P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN11479"
></A
><H2
>Description</H2
><P
>To query the attributes of a modulator applications initialize
the <CODE
CLASS="STRUCTFIELD"
>index</CODE
> field and zero out the
<CODE
CLASS="STRUCTFIELD"
>reserved</CODE
> array of a struct&nbsp;<A
HREF="r11430.htm#V4L2-MODULATOR"
>v4l2_modulator</A
> and
call the <CODE
CLASS="CONSTANT"
>VIDIOC_G_MODULATOR</CODE
> ioctl with a pointer
to this structure. Drivers fill the rest of the structure or return an
<SPAN
CLASS="ERRORCODE"
>EINVAL</SPAN
> error code when the index is out of bounds. To enumerate all modulators
applications shall begin at index zero, incrementing by one until the
driver returns <SPAN
CLASS="ERRORCODE"
>EINVAL</SPAN
>.</P
><P
>Modulators have two writable properties, an audio
modulation set and the radio frequency. To change the modulated audio
subprograms, applications initialize the <CODE
CLASS="STRUCTFIELD"
>index</CODE
> and <CODE
CLASS="STRUCTFIELD"
>txsubchans</CODE
> fields and the
<CODE
CLASS="STRUCTFIELD"
>reserved</CODE
> array and call the
<CODE
CLASS="CONSTANT"
>VIDIOC_S_MODULATOR</CODE
> ioctl. Drivers may choose a
different audio modulation if the request cannot be satisfied. However
this is a write-only ioctl, it does not return the actual audio
modulation selected.</P
><P
>To change the radio frequency the <A
HREF="r11094.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_S_FREQUENCY</CODE
></A
> ioctl
is available.</P
><DIV
CLASS="TABLE"
><A
NAME="V4L2-MODULATOR"
></A
><P
><B
>Table 1. struct <CODE
CLASS="STRUCTNAME"
>v4l2_modulator</CODE
></B
></P
><TABLE
BORDER="0"
FRAME="void"
WIDTH="100%"
CLASS="CALSTABLE"
><COL
WIDTH="25%"
TITLE="C1"><COL
WIDTH="25%"
TITLE="C2"><COL
WIDTH="50%"
TITLE="C3"><TBODY
VALIGN="TOP"
><TR
><TD
>__u32</TD
><TD
><CODE
CLASS="STRUCTFIELD"
>index</CODE
></TD
><TD
>Identifies the modulator, set by the
application.</TD
></TR
><TR
><TD
>__u8</TD
><TD
><CODE
CLASS="STRUCTFIELD"
>name</CODE
>[32]</TD
><TD
>Name of the modulator, a NUL-terminated ASCII
string. This information is intended for the user.</TD
></TR
><TR
><TD
>__u32</TD
><TD
><CODE
CLASS="STRUCTFIELD"
>capability</CODE
></TD
><TD
>Modulator capability flags. No flags are defined
for this field, the tuner flags in struct&nbsp;<A
HREF="r12342.htm#V4L2-TUNER"
>v4l2_tuner</A
>
are used accordingly. The audio flags indicate the ability
to encode audio subprograms. They will <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>not</I
></SPAN
>
change for example with the current video standard.</TD
></TR
><TR
><TD
>__u32</TD
><TD
><CODE
CLASS="STRUCTFIELD"
>rangelow</CODE
></TD
><TD
>The lowest tunable frequency in units of 62.5
KHz, or if the <CODE
CLASS="STRUCTFIELD"
>capability</CODE
> flag
<CODE
CLASS="CONSTANT"
>V4L2_TUNER_CAP_LOW</CODE
> is set, in units of 62.5
Hz.</TD
></TR
><TR
><TD
>__u32</TD
><TD
><CODE
CLASS="STRUCTFIELD"
>rangehigh</CODE
></TD
><TD
>The highest tunable frequency in units of 62.5
KHz, or if the <CODE
CLASS="STRUCTFIELD"
>capability</CODE
> flag
<CODE
CLASS="CONSTANT"
>V4L2_TUNER_CAP_LOW</CODE
> is set, in units of 62.5
Hz.</TD
></TR
><TR
><TD
>__u32</TD
><TD
><CODE
CLASS="STRUCTFIELD"
>txsubchans</CODE
></TD
><TD
>With this field applications can determine how
audio sub-carriers shall be modulated. It contains a set of flags as
defined in <A
HREF="r11430.htm#MODULATOR-TXSUBCHANS"
>Table 2</A
>. Note the tuner
<CODE
CLASS="STRUCTFIELD"
>rxsubchans</CODE
> flags are reused, but the
semantics are different. Video output devices are assumed to have an
analog or PCM audio input with 1-3 channels. The
<CODE
CLASS="STRUCTFIELD"
>txsubchans</CODE
> flags select one or more
channels for modulation, together with some audio subprogram
indicator, for example a stereo pilot tone.</TD
></TR
><TR
><TD
>__u32</TD
><TD
><CODE
CLASS="STRUCTFIELD"
>reserved</CODE
>[4]</TD
><TD
>Reserved for future extensions. Drivers and
applications must set the array to zero.</TD
></TR
></TBODY
></TABLE
></DIV
><DIV
CLASS="TABLE"
><A
NAME="MODULATOR-TXSUBCHANS"
></A
><P
><B
>Table 2. Modulator Audio Transmission Flags</B
></P
><TABLE
BORDER="0"
FRAME="void"
WIDTH="100%"
CLASS="CALSTABLE"
><COL
WIDTH="38%"
TITLE="C1"><COL
WIDTH="12%"
TITLE="C2"><COL
WIDTH="50%"
TITLE="C3"><TBODY
VALIGN="TOP"
><TR
><TD
><CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_MONO</CODE
></TD
><TD
>0x0001</TD
><TD
>Modulate channel 1 as mono audio, when the input
has more channels, a down-mix of channel 1 and 2. This flag does not
combine with <CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_STEREO</CODE
> or
<CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_LANG1</CODE
>.</TD
></TR
><TR
><TD
><CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_STEREO</CODE
></TD
><TD
>0x0002</TD
><TD
>Modulate channel 1 and 2 as left and right
channel of a stereo audio signal. When the input has only one channel
or two channels and <CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_SAP</CODE
> is also
set, channel 1 is encoded as left and right channel. This flag does
not combine with <CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_MONO </CODE
> or
<CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_LANG1</CODE
>. When the driver does not
support stereo audio it shall fall back to mono.</TD
></TR
><TR
><TD
><CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_LANG1</CODE
></TD
><TD
>0x0008</TD
><TD
>Modulate channel 1 and 2 as primary and secondary
language of a bilingual audio signal. When the input has only one
channel it is used for both languages. It is not possible to encode
the primary or secondary language only. This flag does not combine
with <CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_MONO </CODE
> or
<CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_STEREO</CODE
>. If the hardware does not
support the respective audio matrix, or the current video standard
does not permit bilingual audio the
<CODE
CLASS="CONSTANT"
>VIDIOC_S_MODULATOR</CODE
> ioctl shall return an <SPAN
CLASS="ERRORCODE"
>EINVAL</SPAN
> error code
and the driver shall fall back to mono or stereo mode.</TD
></TR
><TR
><TD
><CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_LANG2</CODE
></TD
><TD
>0x0004</TD
><TD
>Same effect as
<CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_LANG1</CODE
>.</TD
></TR
><TR
><TD
><CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_SAP</CODE
></TD
><TD
>0x0004</TD
><TD
>When combined with <CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_MONO</CODE
> the first channel is encoded as mono audio, the last
channel as Second Audio Program. When the input has only one channel
it is used for both audio tracks. When the input has three channels
the mono track is a down-mix of channel 1 and 2. When combined with
<CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_STEREO </CODE
> channel 1 and 2 are
encoded as left and right stereo audio, channel 3 as Second Audio
Program. When the input has only two channels, the first is encoded as
left and right channel and the second as SAP. When the input has only
one channel it is used for all audio tracks. It is not possible to
encode a Second Audio Program only. This flag must combine with
<CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_MONO</CODE
> or
<CODE
CLASS="CONSTANT"
>V4L2_TUNER_SUB_STEREO</CODE
>. If the hardware does not
support the respective audio matrix, or the current video standard
does not permit SAP the <CODE
CLASS="CONSTANT"
> VIDIOC_S_MODULATOR</CODE
> ioctl
shall return an <SPAN
CLASS="ERRORCODE"
>EINVAL</SPAN
> error code and driver shall fall back to mono or stereo
mode.</TD
></TR
></TBODY
></TABLE
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN11598"
></A
><H2
>Return Value</H2
><P
>On success <SPAN
CLASS="RETURNVALUE"
>0</SPAN
> is returned, on error <SPAN
CLASS="RETURNVALUE"
>-1</SPAN
> and the <CODE
CLASS="VARNAME"
>errno</CODE
> variable is set appropriately:</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><SPAN
CLASS="ERRORCODE"
>EINVAL</SPAN
></DT
><DD
><P
>The struct&nbsp;<A
HREF="r11430.htm#V4L2-MODULATOR"
>v4l2_modulator</A
>
<CODE
CLASS="STRUCTFIELD"
>index</CODE
> is out of bounds.</P
></DD
></DL
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